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Quiz

Quiz. a. Why is LOOK better than SCAN? Answer the following two questions using exactly one of the words FCFS, SSTF, SCAN, LOOK, C-SCAN, C-LOOK b. Which algorithm possibly results in starvation? c. Which of SCAN or C-SCAN gives better throughput?. Where is RAID, or is SSTF implemented?.

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Quiz

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  1. Quiz • a. Why is LOOK better than SCAN? • Answer the following two questions using exactly one of the words FCFS, SSTF, SCAN, LOOK, C-SCAN, C-LOOK • b. Which algorithm possibly results in starvation? • c. Which of SCAN or C-SCAN gives better throughput?

  2. Where is RAID, or is SSTF implemented? • OS* … disk • cheap … expensive • older … newer • serial … parallel (offload work and complexity) • logical … physical • volume: logical disk; may span physical disks, or may have several volumes on a physical disk • OS must keep track of physical disks to do * above. • Third alternative in middle is possible: • OS … controller card (host bus-adapter) … disk

  3. Excerpt from Chapter 13

  4. How Does Plug and Play (PnP) work? • Reassigns port and maskable interrupt to avoid collision with another device. • Port: device register mapped to small amount of memory to provide control information. • (Contrast: Memory-mapped device, where large amount of memory provides data to or from the hardware.) • MIRQ and NMIRQ wires provide interrupt number, telling what interrupt occurred, provided by the CPU. • (Contrast: Interrupt level, which is a priority set by OS.)

  5. Device I/O Port Locations on PCs (partial)

  6. Pentium maskable vs. non-maskable interrupts

  7. Windows XP Interrupt Request Levels

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